Fifty-five years ago Sanford Greenberg was 20, newly blind through bad luck and misdiagnosis, and rightly angry at the world when he made a vow from his hospital bed. “No one should have to go blind,” he thought. “It was a promise I made not just to myself but to God.”

It was, and remains, an enormous aspirational pledge. Around the world 39 million people—roughly one out of 200—are blind, as writer David Dobbs and photographer Brent Stirton reveal in this month’s cover story. Another 246 million are moderately or severely visually impaired. The human costs are staggering, both for those with vision loss and for the hundreds of millions of people who assist them.

Greenberg is one of the fortunate ones. In 1961 he ignored the social worker who suggested he go home to Buffalo, New York, and make cane-backed chairs in a program for the blind. Instead, with the aid of the college roommate who read textbooks to him and helped him get around campus, Greenberg finished his bachelor’s degree at Columbia. He earned a doctorate at Harvard. He worked at the White House. He helped create a device that made listening to recorded speech more convenient for blind people—and made him financially independent in the process. He serves on boards and commissions too numerous to name. He married Sue, whom he’d loved since sixth grade; they are married still. And he remains close friends with that Columbia roommate, who studied architecture but pursued a career in music: Art Garfunkel, of Simon & Garfunkel fame.

“Clinical relief of blindness … appears to stand at a point rather similar to that of the nascent American program of space exploration in the 1950s and early 1960s,” Greenberg says. “Practically waiting.”

Worldwide, half of all blind people lose their sight to cataracts—routinely fixed in the developed world but a tragically common cause of blindness in the developing one. Meanwhile other approaches are advancing rapidly, as our coverage explains: gene and stem cell therapies, bionic implants.

How does Greenberg regard all this? “My determination has not faltered,” he says. “Blindness is an injustice—‘unfair,’ we say in our plainspoken American way. We must act to end it.”